Question about the Fin Tank

[vololiberista]

I'm curious about the fuel management regarding the fin tank.
Do you / Did you? Always set off from base with a full fin tanlk or partially full tank?
If so do you/did you have a minimum fuel level?
It would appear from the manuel that a minimum of 50kgs "must" be in the tank for landings.
vololiberista

[Tonkenna]

The fin tank did not have to be filled (unless you got to a fuel load figure that required it)... I don't have the tables to hand to be able to tell you when, on standard lading fuel would go in there. Th 50 kg was a max for landing... Obviously in an emergency you could land with fuel up there, but for normal landings the max was 50.... You didn't have to land with 50 in there!

Tonks

[vololiberista]

The fin tank did not have to be filled (unless you got to a fuel load figure that required it)... I don't have the tables to hand to be able to tell you when, on standard lading fuel would go in there. Th 50 kg was a max for landing... Obviously in an emergency you could land with fuel up there, but for normal landings the max was 50.... You didn't have to land with 50 in there!

Tonks

Thanks Tonks,
I suppose then it would not be filled unless one had a long leg then. I was curious because I was wondering if its purpose was just to adjust the trim as in Concorde. clearly with a load of fuel it would have an effect which is why the 50kg max on landing is set.

[Gwyn]

In BA used the fin fuel to sort of balance the trim. It was a bit of a crude attempt and I never did know whether it was effective or not. I remember once the F/E was playing with his fuel balancing via the jettison panel and dumped the fin fuel all over Shannon heading west to JFK. Drinks all round in the end plus a lot of log fiddling to account for the loss of fuel.

[Jelle Hieminga]

There is only one fuel pipe running from the fin tank to the centre tank and three valves that allow fuel to be transferred that way. You cannot (if I'm not mistaken) transfer fuel in flight to the fin tank. Because of that there is no real way to control the CG using your fin tank, you can only delay the transfer to the centre tank.


From: http://www.vc10.net/Technical/fuel_system.html

Active CG control using fuel only came about on Concorde and later on MD-11 and Airbus models. The A340 for example transfers fuel to the horizontal stabiliser tank early in the flight and keeps it there as long as possible for economy reasons. On the Concorde the reason for the fuel transfer is not economy but the fact that the centre of lift moves rearward when you go supersonic.

[Gwyn]

That is correct. you can only take fuel from the fin and not the other way round. What the F/E did was to drop the fin fuel to a pre-determined level according to a chart when first in the cruise and then transfer it all 1 hour from landing. There was, if I recall, a slow and fast transfer valve to get the fuel out of the fin. My man in question opened the fin dump valve by accident and off it went overboard. He became distracted like any good F/E by a plate of food just delivered. If you look at the rear end of super you will see a small vent valve between the engines.

[vololiberista]

That's interesting that you can't "replenish" the fin tank in flight. The manuel is certainly not clear on that point as it states procedures for adding and taking fuel from the fin tank without saying not in the air.
Having said that, presumably the fin tank could be replenished from the centre tank on the ground (as there is only one pipe)?
What sort of fuel loads required the filling of the fin tank?

vololiberista

[Gwyn]

The refuel panel, if I am correct, allowed the Fin to be filled direct from the bowser. It was only when high fuel loads were needed that the fin was ever filled. I believe the capacity was about 2.5 - 3.0 tonnes and on a LHR-JFK then this fuel became the holding fuel available at JFK (about 20-25 mins. if my memory serves me well).

[Laurieg]

The fin tank is fed from the main fuel gallery. It has a normal inlet valve identical to all the other ones in the system so if you can get fuel into the gallery you can get fuel into the fin. On the ground this is achieved by selecting the tank open on the FLCP with the gang bar down. Obviously, in flight this is in the up position due to the access panel being closed. This action of the gang bar passes power from the FLCP to panel B where all of the inlet valves can be operated, either on the ground or in the air.

The fuel feed to the fin tank enters the same pipeline up stream of the 3 transfer valves therefore you can put fuel up that way but it can only come back down to the centre via the 3 trans valves.

Fuel can be transferred up to the fin in flight, as I have seen often, normally for trim purposes in the cruise. This is achieved in the way above except that it is under the control of the Trim Alert system. On the centre and fin tank gauges on panel B there are 2 pointers, one is yellow and the other is the normal contents indicator. When transferring fuel up to the fin the FE will dial up the amount he wants there on the yellow pointer and he will 'dial down' the same amount he wants out of the centre tank using that yellow cursor. When he selects the inlet and fin isolate valves to open he can pump it there. When the transfer is complete and both tank content cursors are aligned the TA attention getters flash to tell the FE the transfer is complete. The same can be done in reverse but this time using one of the transfer valves that is under control of the system and will close instead.

The inlet valve power supply is routed via the cursors so that it is removed and the valve closes on completion.

I believe I have got that right from memory but will check in the books when I get back from Cyprus next week. [-o<

[vololiberista]

Thanks Laurie,
Your description matches pretty much to what the manuel says. as it makes no mention of not being able to transfer fuel to the fin tank in flight as has been mentioned above.
vololiberista

[Gwyn]

I stand corrected about the transfer of fuel to the fin in flight. I chatted to an old F/E friend of mine who I flew with on the VC-10 and he confirmed exactly what you say. I think, maybe, I was getting confused with the 747-400 stab fuel which definitely cannot receive fuel in flight. As life goes by it gets more confusing sometimes.

[Manofmendip]

Well done Laurie

The supreme technical custodian of the VC10.

Best wishes and see you soon I hope.

Dave

[Laurieg]

On a similar subject. If you want the aircraft refuelled to max for a long run you can refuel the ac to max shutoff on the float switches. You then trans via the fast/slow 1/4A trans valves until the vent tank pump runs ( not under any float switch control). That is the wing tanks full. You then trans fuel down from the fin into the centre via the slow trans valves (not under centre tank float switch control) until that vents. You then try to trans out to the wings until they vent. Drop any fuel you can out of the fin into the centre and then refuel the fin until that vents. You cannot refuel the aircraft anymore! Used to do it at Ascension Island all the time on navexes. Handlers were not very happy though swith mess you left though

[Tonkenna]

Ahhhh... there was nothing like seeing the panic on the faces of the USAF ground crews when you guys got a VC10 venting! Seen it a few times, once or twice at Asi as you said!!!

Tonks

[Laurieg]

I bet you flt deck crews wondered how we did it! The chats we used to have with the FE were always interesting! One used to ask for the FULL 1/2 per cent whether it was or not.